1. Field of the Invention
The present invention relates to pipe fittings employing split-clamp type couplings and particularly to piping wall castings for use with such couplings.
2. Description of the Prior Art
The type of piping connectors known in the trade as wall castings are fittings intended to be preplaced in poured concrete walls where pipe penetrations are required. After the concrete has set and the forms have been stripped, continuing piping is then coupled to the wall casting on one or both sides of the wall. Such wall castings are used extensively in water filtration and sewage treatment plants, in sizes ranging from 4 to 48 inches.
In order to connect the continuing piping, wall castings are typically supplied either with plain bolting flanges or with bell ends. The plain flanges are usually drilled and tapped for studs to allow a similarly flanged continutation pipe to be bolted on. Although a flanged connection is inexpensive and easy to assemble and disassemble, it requires precise alignment of the continuation piping with the wall casting, or the joint will leak.
On the other hand, a bell end coupling, which is technically termed a mechanical-joint connection, will accomodate approximately 2.degree. to 5.degree. of angular misalignment at the joint. A mechanical-joint coupling is assembled by inserting a plain end of one pipe section into a bell end of another pipe section or fitting, after first slipping a flanged gland and a rubber gasket over the plain end. The gasket fits inside the bell and is maintained in compression by bolting the flange of the gland to a mating flange on the bell end. A drawback to the mechanical-joint type of connection, however, is that the joint is held together only by the friction between the rubber gasket and the inner pipe that results from the pressure exerted on the gasket by the gland.
A third type of commonly used coupling is a split-clamp type known as a Victaulic coupling, after the manufacturer. This coupling combines the advantage of a mechanically secure joint, as provided by flanged couplings, with the ability to tolerate several degrees of angular misalignment, as provided by mechanical-joint couplings. It comprises a resilient gasket, which bridges two butted pipe ends, and a split clamp in the form of two semicircular shells which, when bolted together, sealingly compress the gasket against the circumference of each pipe end.
To accept this coupling, each pipe is formed with a circumferential groove spaced a short distance from the end or, in the larger sizes, with a circumferential shoulder located at the end. The split-clamp shells each have a U-shaped cross section. The sides of the U face inward, enclosing and compressing the gasket against the pipe and also engaging the groove or the shoulder to lock the butted pipe ends together. Thus, the split-clamp type of coupling is simple and easy to assemble.
Because the gasket and clamp fit around the outside of the pipe ends, however, this coupling can be used only where there is sufficient clearance around the joint for installation and removal. Consequently, there has been little application of split-clamp type couplings to wall castings, in spite of their many advantages. It has always been considered necessary for the pipe ends to extend beyond the sides of the finished wall so that they would be accessible for mounting the gasket and clamp. This means cutting holes in the forms, which then must be repaired before they can be used again at a different location. If repair proves too expensive, the forms must be discarded.
In addition, it is often required that the pipe line continuing from the wall casting be installed close to the wall to simplify pipe hanger requirements and also to take up less space. If the wall casting joint is displaced several inches out from the wall, this requirement cannot be met, at least not without additional pipe fittings,.